Nord Polar Night theme created using the Sublime json-based theme and the TM Theme editor.
To download and apply the theme.
> rstudioapi::addTheme("https://raw.githubusercontent.com/siegerts/rstudio-nord-theme/master/Nord.tmtheme", apply = TRUE)
More information regarding creating your own theme or customizing an existing one can be found at https://rstudio.github.io/rstudio-extensions/rstudio-theme-creation.html